An explosive assembly including a body portion and a closure having a covering of elastomeric material

ABSTRACT

This invention relates to an explosive assembly having a body portion and closures therefor, the body portion and closures having a covering of an ablative elastomeric material where the elastomeric material is polybutadiene acrylonitrile, polychloroprene and mixtures thereof with polyvinyl chloride that is compounded with a curative, plasticizer and a burn resistant agent, preferred plasticizers being phenol formaldehyde resin or polyethylene of 8,000 to 15,000 molecular weight.

United States Patent Evans et al. 1 Jan. 18, 1972 EXPLOSIVE ASSEMBLY References Cited INCLUDING A BODY PORTION AND A UNITED STATES PATENTS CLOSURE HAVING A COVERING OF ELASTOMERIC MATERIAL 2,678,293 5/1954 McMillan et a1. ..260/2.5 F 2,683,697 6/1954 Newell et al ...260/2.5 F [72 lnvenmm TM" Evans; Marvin Conger, 3,401,253 10/1968 Yoshimura ..260/889 both of Akron, Ohio 3,429,838 2/1969 Hersh ..260/2.5 SI 1 Assignw The Goodyear Tire & Rubber Company, Primary ExaminerMurray Tillman Akmn Assistant Examiner-Morton F oelak [22] Filed: Dem 24, 1968 An0mey-F. W. Brunner and J. D. Wolfe [21] Appl. No.: 786,666 [57] ABSTRACT This invention relates to an explosive assembly having a body [52] US. Cl. ..260/2.5 FP, 102/105, 260/25 R, portion and closures therefor, the body portion and closures P, having a covering of an ablative elastomeric material where 2 /285 B, 26 /28-5 D, 2 /2 R, the elastomeric material is polybutadiene acrylonitrile, 2 /4 845 polychloroprene and mixtures thereof with polyvinyl chloride [51 1 Int. Cl 1/20 that is compounded with a curative plasticize and a bum re- [58] Field of Search ..260/2.5 F, 889; 102/105 sistant agent, preferred plasticizers being phenol formal- V dehyde resin or polyethylene of 8,000 to 15,000 molecular weight.

4 Claims, 2 Drawing Figures g. l l \IO PATENTED JAN] 81972 3 K I I I I I 1 I 1 1 I u n I I. III... 2 I 1 n I Q X. n n o m I I a 7 a. o

INVENTQRS MARVIN CONGER E A.EVANS ATTORNEY EXPLOSIVE ASSEMBLY INCLUDING A BODY PORTION AND A CLOSURE HAVING A COVERING OF ELASTOMERIC MATERIAL This invention relates to a protective cover for apparatus and equipment to be protected from high temperature. More particularly, this invention relates to protective covers for fuel or solvent storage tanks and container-type explosives including bombs and rockets and to the method of making and providing the protective cover for said shells or equipment including the protective compositions.

Shells, bombs and other container-loaded explosives have to be handled and stored until they are used and this storage and handling presents a safety problem. This safety problem is particularly aggravated when fire breaks out in the vicinity of the ammunition or fuel storage area. It is particularly desirable that some means be provided to protect fuel, shells or bombs from immediate ignition or explosion upon contact with fire, for instance, if a few minutes protection is provided it frequently provides sufficient time to isolate the fire or to confine the hazard of the explosive from the fire.

Therefore, an object of this invention is to provide a protective cover for apparatus or equipment, shells, bombs, rockets and related container filled explosives to protect them from fire to thereby increase the time available to isolate the fire hazard.

This object and other advantages of this invention can more readily be seen by reference to the drawings wherein FIG. 1 is a longitudinal cross-sectional view through a bomb and FIG. 2 is a cross-sectional view along the line 22 of FIG. I.

In the drawing, numeral 3 represents in general a shell or bomb having a metal casing 4, an explosive mixture 5 therein and a detonating means 6 at the end of the shell. Normally a covering 13 of asphalt, wax or resin is applied to the inside of the casings to protect the explosive from shock, etc. Numeral 7 represents a cap member containing a firing or aiming mechanism with electrical lead-in or lines 8 and plug-in 9 for the lines. Thus, in general it can be said that the explosives of FIGS. 1 or 2 represent a typical shell or bomb. Numeral l designates the protective coating which encapsulates the metal casing 4 of the shell. Referring to FIG. 2 it will be noted that the protective covering 10 in this embodiment has a zipper-type means II to open the protective cover and permit its removal from the shell just prior to the time the shell is to be fired or used. Alternately, the protective cover may be adhered tightly to the shell and may be fired with the protective cover around the shell except this embodiment may have a tendency to reduce the impact or fragmentation velocity upon explosion of the shell. Likewise, the protective covering may reduce the scatter where a fuel storage tank explodes or burns.

The protective cover may be fabricated as an envelope, as indicated above, and thus be wrapped or taped tightly around the shell or ultimately it may be equipped with zipper-type means or even buttons or other fastener means to permit the cover to be placed on the shell and attached to the shell with the desired degree of rigidity.

The protective cover in one embodiment is prepared by compounding suitable elastomeric materials with suitable compounding agents to give a protective cover which has sufficient burn resistance to insulate the shell or bomb from heat or burning therethrough for several minutes and preferably for to minutes when exposed to a flame such as that of an ordinary laboratory gas burner. The compounding of the rubber may be achieved on a mill or a banbury and then the compounding material is sheeted out on a calendar, preferably to a thickness of about one-sixteenth to one-half of an inch with the preferred thickness being about one-eighth to three-sixteenth of an inch. This sheeted material then is cut to appropriate dimensions for the size shell or bomb to be covered. This sheeted material is then wrapped around the shell and pressed into tight contact around the shell in the various curved or tapering portions to obtain a tight fit in the wellknown manner of laying up of rubber sheet over a form. In this instance it should be emphasized that the shell serves as a form enu- e s?! ithei smqsq lein laying up the rubber to achieve the desired contact and fit of the protective cover on the shell.

In those instances where the shell and the protective cover are not to be separated it is desirable to place the protective cover on the metal casing of the shell and then the protective cover is cured around the shell with the desired accessory opening such as for adding fuses or electrical plug-ins, in the instance of a bomb. With the shell containing the protective cover cured thereon the shell then can be filled in the normal manner with the explosive. The filling opening of the shell containing a protective cover is closed in the usual manner with a cap or plate, preferably the cap or plate also contains a covering of this protective material to insulate or protect it from the fire.

Where the missile is in fact a bomb, with fins 12 to stabilize its fall or flight, it is preferred that the fins also be covered with the protective material as part of the protective cover for the missile.

Representative of materials that can be used for making the protective cover are those showing in the following representative examples ,where all parts are by weight unless otherwise designated.

EXAMPLEI The ingredients in the recipes of table I were compounded in a Banbury mill and then the stock was fed to a calendar mill *to form the stock into sheets 0.030 inches by 13 inches wide and wrapped on a 3% inch O.D. aluminum mandrel covered with cellophane foil to give a covering having 0.60-inch oversize gauge. The covering was then wrapped with a wet nylon curing tape and cured in an autoclave for 30 minutes at 325 F. Since the protective cover on the aluminum mandrel was oversize it was turned down on a lathe to give a protective cover of 0.125 inches thick. The rubber sleeve or protective cover was removed from the mandrel and placed or mounted on a 3% inch CD. by 12-inch steel pipe having thermocouple leads placed therein to measure the temperature of the pipe during the fire testing of the cover. The steel pipe with protec- ;tive cover was then subjected to a jet fuel fire test where heat input to the protective cover was 40,000 B.t.u. per hour per square foot and the time to reach explosive temperature mea- TATSLE I Boreeic acid Tetra methyl thiuram disulflde Total 220.50 295.60 310.00 315.60 300.50 300.50

1 The chlorinated wax in these examples had a 40% chlorine content whereas the chlorinated wax used in the other samples had a 70% chlorine eonten 1 Oncor 23A is a mixture of 50% antimony oxide with silicon oxide precipitated thereon.

V The jet fuel fire test results are shown in table II: m

Table II Recipe No. Protection time, minutes C-4 C- l 7 EXAMPLE ii 1 and sheeted out. Tensile sheets were cut from these sheets and subject to burn test described in table IV to determine seconds EXAMPLE lii Test samples were made by compounding the ingredients according to recipe numbers shown in table V in a Banbury mill and sheeting. The test specimen (4.5"X4.5" 0.070)

5 required for tensile sheet to reach 288 F. The results of these were from the sheet and Subjected to a bum test In a Flsher te t are ho in t bl IV, burner at a flame temperature of i,600 F. and timed to reach 288 F. as indicated by a 288 F. thermal stick, was observed.

TABLE IH' COVER COMPOUND FORMULATIONS The results of these burn tests are tabulated in table V. It Recipe Number C3I 04-1 039 C40 should be noted that the protective efl'iciency of the covering Neoprene GNA 100,0 m0 10M 10M has n mo e than double where the recipe contains a ther- ISjtearie acid 5.3 3.5 3.3 6.8 moplastic phenol formaldehyde resin. For instance, compare gff i zig III" I 2: g tChe3 D011: testshon samplesI 37 to with thotse for samples or 110 0X 9 us, t e use 0 to parts 0 a two-stage theri iigfl iigiiiil ifgifiel fffit??? 3:8 3:8 518 5 15 moplastic phenol formaldehyde resin, preferably without a Boracigacid 550.0 8gb 80.0 80.8 phenol formaldehyde curative, with each I00 parts of gflfg gg f jg fl? F; Neoprene compounded with cun'ng agents, fillers and exten- Chlorinated polyethylene 20.0 1 ders for said Neoprene, gives a protective cover which offers Tomi 3m 5 3m 5 350, 5 5 5 improved protection from the sudden heat rises occasioned by 2 20 EXEQE- P TABLE V Recipe Number 47 48 49 50 61 52 63 54 55 66 57 58 Neoprene GNA Stearic acid Magnesium oxide. Zinc oxide Phenyl beta naphthylamine Oncor 23A Z-mercaptoimidazoline. Chlorinated wax Durez 13037... Boracic acid.- 21.0 80.0 Sym-B-naphthyl-p-phenylenediamine 2.0 Durez 11504 Polyethylene, low rn.w. Chlorinated polyethylene 5.0 10.0 10.0 Chlorinated wax 15.0 30.0 45.0 Burn test, seconds: Trial Number:

Recipc C15 0 Also, it should be noted that use of about one to six, preferably about two to four parts of a polyethylene, having a Polyvinyl chloride molecular weight of 8,000 to 15,000 and preferably 10,000 to 67/33 Butadiene acrylonitrile polymer Mooney 70 50.0 further enhances the protection afforded y t Barium cadmium zinc vinyl stabilizer l.4 Hydrogenated soya fatty acid 01 cover. A comparison of burn tests on run 52 indicates nearly a Vinyl stabilizer 0.2 45 fifty percent improvement. Epoxy soya oil plasticizer 1.5 iHflmflm W W""" A Trici'csyl phosphate 25.0 Oncor 23A 00 EXAMPLE lV 32:33:12; 3 The sample specimens 4.5" 4.5"X0.070" were made on the stocks identified as recipes No. 25 and C-l7. These sam- BURN TEST RESULTS The burn test was conducted in a l,600 F. flame of a Fisher burner. Results in the table are seconds to 288 F." Burn test sample was a 0.0750.079" thick tensile sheet of the respective compounds. A 288 F. Tempil stick was used to mark the tensile sheets and indicate the temperature. It should be noted that the burn test sheets had been cured for 60 minutes at 324 F. before being subjected to the burn test.

Table IV Seconds to 288 F.

ples were marked with a 288 F. Tempel stick (a temperatureindicating crayon) and placed in the flame of a Fisher burner at a temperature of 1,600 F. and the time in seconds required for the samples to reach 288 F. was noted.

Another group of these sample specimens were placed in a hot air oven at 325 F. for one hour to cure. The sample specimen expanded to 7" 7.5"X0.350". The cooled cured samples were subjected to the burn test and time required for the samples to reach 288 F. noted. The results of these tests are shown in table VI.

Table VI -lfi filfi- -91? Burn test, See.

Before cure i4 24 After cure 330 200 5 6 made using recipes Nos. 18 and i9 arecornpared with Nos. 20 The chlorinated polyethylene (in table Vll) marked conand 21 it will be noted that the curing of samples 20 and 2] tained 25 to 30 percent chlorine, whereas others contained l with a blowing agent such as aziodicarbonamide gave approxito 20 percent.

mately a 50 percent improvement in burn resistance. Thus, The foregoing examples and disclosure indicates an ablative use of about 0.5 to 10 parts and preferably one to seven parts elastomer of about 50 to 400 mils, and preferably 100 to 300 of a blowing agent such as azobisformamide, azobisisobumils, on a metallic body such as steel, copper, bronze, alutyronitrile, diazoaminobenzene, N,N'-dimethyl-N,N'- minum and related body materials reduces the heat transmisdinitrosoterephthalamide, N,N-dinitrosopension and thus delays the time an explosive mixture reaches the tamethylenetetramine, benzenesulfonyl-hydrazide, toluenel0 explosive limit from heat. (4)-sulfonyl hydrazide, benzene-1,3-disulfonyl hydrazide, While certain representative embodiments and details have diphenylsulfon-3,3-disulfonyl hydrazide, 4,4 '-oxbeen shown for the purpose of illustrating the invention, it will ybis(benzenesulfonyl hydrazide), or the lower boiling solvents be apparent to those skilled in this art that various changes in the protective cover enhances the degree of porosity of the and modifications may be made therein without departing cured or finished cover and thus improves the covers protecl 5 from the spirit or scope of the invention. tive ability relative to fire. What is claimed is:

' 1. An explosive assembly including a body portion and clo- TABLE VII sures therefor, said body portion and closure having a cover- Bc BC BC ing of 50 to 400 mils of elastomeric material on the outside ip Number 14 15 16 17 18 19 20 21 20 surface thereof, said covering material being characterized by a burn resistance sufficient when a specimen 4.5"X4.5 "X 0.070" is subjected to a flame of about l,600 F. from a Fisher burner, the time for the side opposite the flame to reach 288 Polyvinyl chloride. 50. 0 67/33 butadiene aerylonitrile polymer 50.0 Barium cadmium zinc vinyl stabilizer 1.4 F. being 13.8 seconds or longer, said elastomeric material {;;%;;3f j{ f?jf 0' 2 25 being selected from the class of \inyl stabiiizialr 0.2 A. a copolymer of acrylonitrile-butadiene,

33.33;? pq y p a Tricresyl phosphate 25.0 25. 0 C. mixtures of (A) with polyvinyl chloride. i'gfi poly 2. The assembly of claim 1 wherein the elastomer is com- Oncor 23A... pounded with a two-stage phenol formaldehyde resin. Boracic acid.

Carbon 3. The assembly of claim 1 wherein the elastomeric material Aziodicarbonamid e IS porous. gg ffg g w 4. The assembly of claim 1 wherein the elastomer is com- 0 22.1 24.0 24.2 28.7 21. 9 19.0 30.1 32.6 pounded with about 1 to 6 percent by weight of a polyethylene No 2 21.8 23.8 24.1 28.9 22.0 19. 2 .8 .0 35 g oo to 5 000 mo] ulalweight TABLE VIII Recipe Number 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 Neoprene GNA; 100 Stearic acid Durez l2687 Magnesium oxide- Zine oxide Boric anhydride. Antimony oxide 2 mercaptoimldazoline Poly-B-chloroethyl triphosphonate. Chlorinated polyethylene Oncor 23A 5813 mmlo n-mo 

2. The assembly of claim 1 wherein the elastomer is compounded with a two-stage phenol formaldehyde resin.
 3. The assembly of claim 1 wherein the elastomeric material is porous.
 4. The assembly of claim 1 wherein the elastomer is compounded with about 1 to 6 percent by weight of a polyethylene of 8,000 to 15,000 molecular weight. 